Check valves are very common piping fittings which are used to prevent back flow within a run of pipe. A check valve has a body with a hinged flapper disposed inside. The body and the flapper are adapted so that, when back flow occurs within the body, the flapper seals against a valve seat within the body, thereby closing the valve.
A lightweight type of check valve frequently used in plastic pipe runs is a check valve having a gasket sandwiched between a flapper base and a flapper cover. The flapper base has a flapper base stem which extends through a central aperture in the gasket and through a central aperture in the gasket cover. The composite, consisting of flapper base, gasket and flapper cover, is typically held together by the cooperation of the flapper base stem with the flapper cover. Typically, such cooperation takes the form of press-fit or snap-on fit, although adhesives and welding are also sometimes used to connect the flapper base stem and the flapper cover.
A problem exists with such check valves when pressurized liquid on the downstream side of the flapper seeps between the flapper base and the gasket when the flapper is in the closed position. Such seepage leads to pressure build-up across the face of the gasket surface which exerts a significant force against the flapper cover. Such force is frequently sufficient to break the connection between the flapper base stem and the flapper cover, causing the flapper to come apart.
Accordingly, there is a need for a check valve which avoids the aforementioned problem in the prior art in an inexpensive and efficient manner.